The Impact of Childhood Measures of Glycemia and Insulin Resistance Factors on Follow-Up Glycemic Measures

Abstract

The purpose of this research was to evaluate the impact of glycemic measures, and changes in identified risk factors (BMI, waist circumference, lipids, blood pressure) on follow-up glycemia, in Pima children at high risk for type two diabetes (type 2 DM).I computed incidence and cumulative incidence of type 2 DM in Pima children 5-19 years of age between 1983 and 2004. Cox proportional hazards rates for development of type 2 DM were calculated by glycemic measure (HbA1C, 20PG, FPG) controlling for confounding factors (age, sex, BMI, blood pressure, and cholesterol). Diabetes was defined by the presence of at least one of four criteria: 1) 20PG of >200 mg/dl, 2) FPG of >126 mg/dl, 3) HbA1C > 8.0%, or 4) hypoglycemic treatment. Linear regression models were computed to identify the impact of changes in risk factors on changes in HbA1C. Only exams performed in non-diabetic children during childhood were included in the regression models.Among 2658 non-diabetic children, 258 cases of diabetes occurred during mean 9.1 years of follow-up (1.5 - 21.7). The age-sex adjusted incident rate of diabetes was 19.0 cases per 1000 person-years, and cumulative incidence was 54% by age 40. Incidence rates increased with increasing baseline values of 20PG, and FPG, but not for HbA1C. For HbA1C the relationship was u-shaped with the lowest and highest quartiles having the highest DM rates. After adjustment for confounding risk factors using Cox proportional hazards analysis, the risk for diabetes increased 2-fold for every 10 mg/dl increase in FPG. Changes in waist circumference best predicted changes in HbA1C (R2 = 0.48, Ï <0.001). However, the ability of waist circumference to predict change is limited due to the powerful effect of regression to the mean, suggesting that these risk factors contribute very little to changes in HbA1C, at least in childhood.Childhood levels of glycemia predict development of type 2 DM later in life. While changes in waist circumference are associated with only moderate changes in HbA1C, this does not refute the significant contribution of adiposity in childhood to the development of type 2 DM.